RE: RMAN question(s)
- From: "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx>
- To: <robertgfreeman@xxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 13 Sep 2007 11:22:01 -0700
Hi Robert, could you please clarify a couple things for me since I've
never tried compressed backupsets?
1) My understanding is that "as compressed backupset" is not recommended
if you're backing up to a tape drive (e.g. LTO3) that is already
performing its own compression. Is that correct?
2) You say compression will save time as well, but I thought that a
compressed backup would actually take longer due to the extra processing
required for the compression. I can't see how it would save time unless
you are on a very IO-bound system such that the extra processing time
for compression is more than compensated for by the reduction in disk
writes (especially if you're backing up to RAID5), or if you are
transferring over the network obviously there would be significant time
savings from the smaller file to transfer. Do you typically find that
the reduction in disk write time outweighs the increased CPU time?
Thanks,
Brandon
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Robert Freeman
Sent: Wednesday, August 29, 2007 6:32 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: RE: RMAN question(s)
Seems you have already gotten some great answers! I might also suggest,
if you are in 10g, that you look at adding compression to your backups
(backup as compressed backupset database plus archivelog delete input).
You might be amazed at how much smaller your backupsets are and how much
time using compression can save on your backups (at the cost of some CPU
of course).
When I do RMAN courses I like to demonstrate a compressed vs.
non-compressed RMAN backup. The compression itself can be impressive,
the time to backup savings can likewise be impressive (Ceteris
paribus.... oooops, can I say
that.....?)
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